Field of the Invention
The invention is directed to electrochemical systems and particularly electrochemical compressor systems.
Background
The function of refrigeration cycles and heat pumps is to remove heat from a heat source, or reservoir at low temperature, and to reject the heat to a heat sink, or reservoir at higher temperature. While many thermodynamic effects have been exploited in the development of heat pumps and refrigeration cycles, one of the most popular today is the vapor compression approach. This approach is sometimes referred to as mechanical refrigeration because a mechanical compressor is used in the cycle.
Mechanical compressors account for approximately 30% of a household's energy requirements and thus consume a substantial portion of most utilities' base load power. Any improvement in efficiency related to compressor performance can have significant benefits in terms of energy savings and thus have significant positive environmental impact. In addition, there are increasing thermal management problems in electronic circuits, which require smaller heat pumping devices with greater thermal management capabilities.
Vapor compression refrigeration cycles generally contain five important components. The first is a mechanical compressor that is used to pressurize a gaseous working fluid. After proceeding through the compressor, the hot pressurized working fluid is condensed in a condenser. The latent heat, of vaporization of the working fluid is given up to a higher temperature reservoir, often called the sink. The liquefied working fluid is then expanded at substantially constant enthalpy in a thermal expansion valve or orifice. The cooled liquid working fluid is then passed through an evaporator. In the evaporator, the working fluid absorbs its latent heat of vaporization from a low temperature reservoir often called a source, The last element in the vapor compression refrigeration cycle is the working fluid itself.
In conventional vapor compression cycles, the working fluid selection is based on the properties of the fluid and the temperatures of the heat source and sink. The factors in the selection include the specific heat of the working fluid, its latent heat of vaporization, its specific volume and its safety. The selection of the working fluid affects the coefficient of performance of the cycle.
For a refrigeration cycle operating between a lower limit, or source temperature, and an upper limit, or sink temperature, the maximum efficiency of the cycle is limited to the Carnot efficiency. The efficiency of a refrigeration cycle is generally defined by its coefficient of performance, which is the quotient of the heat absorbed from the sink divided by the net work input required by the cycle.
Any improvement in refrigeration systems clearly would have substantial value. Electrochemical energy conversion is considered to be inherently better than other energy conversion systems due to their relatively high exergetic efficiency. In addition, electrochemical systems are considered to be noiseless, modular, scalable and can provide a long list of other benefits depending on the specific thermal transfer application.